The present invention relates to a swashplate type variable-displacement compressor, and particularly to a swashplate type variable-displacement compressor serving as a compression part of a refrigerator circuit such as an automotive air-conditioning system, so as to compress refrigerant vapor to a relatively high pressure.
In recent years, there have been proposed and developed various swashplate type variable-displacement compressors in which a valve opening of a pilot valve is controlled depending on a current value of exciting current for an electromagnetic solenoid, in order to act high-pressure refrigerant gas introduced from a refrigerant discharge chamber via the pilot valve having the controlled opening on the back of a piston-shaped spool valve portion for adjustment of axial position of the piston-shaped spool valve portion, and consequently to control the amount of low-pressure refrigerant gas flowing into a refrigerant suction chamber. One such swashplate type variable-displacement compressor has been disclosed in Japanese Patent Second Publication No. 6-89741. The swashplate type variable-displacement compressor disclosed in the Japanese Patent Second Publication No. 6-89741, is basically constructed as a typical swashplate type variable-displacement compressor equipped with a compressor clutch which is a solenoid-type electromagnetic clutch located in a compressor pulley. The clutch equipped swashplate type variable-displacement compressor is complicated in structure. Generally, the clutch equipped swashplate type variable-displacement compressor is comparatively heavy in weight, and also requires many component parts. In addition to the above, when the amount of low-pressure refrigerant gas flowing from the evaporator outlet into the refrigerant suction chamber of the compressor must be adjusted to xe2x80x9c0xe2x80x9d to prevent icing of the evaporator core during operation of the swashplate type compressor with the compressor clutch engaged, the magnitude of exciting current of the electromagnetic solenoid which is used to actuate the pilot valve is generally controlled to the maximum so as to move the piston-shaped spool valve portion to a fully-closed position corresponding to the maximum length of the piston-shaped spool valve stroke, thus resulting in increased electric power consumption.
Accordingly, it is an object of the invention to provide a swashplate type variable-displacement compressor, which avoids the aforementioned disadvantages.
It is another object of the invention to provide a lightweight, clutchless swashplate type variable-displacement compressor, which is capable of being switched between operative (ON) and inoperative (OFF) states without using a compressor clutch, and of controlling evaporator icing by demagnetizing an electromagnetic solenoid used to operate a pilot valve (capable of controlling the flow of refrigerant from the evaporator outlet to a refrigerant suction chamber of the compressor) for the purpose of adjustment of the amount of low-pressure refrigerant gas flowing into the refrigerant suction chamber to xe2x80x9c0xe2x80x9d.
In order to accomplish the aforementioned and other objects of the present invention, a swashplate type variable-displacement compressor comprises a compressor housing which defines therein a crank chamber, a refrigerant suction chamber, a refrigerant discharge chamber, and a low-pressure refrigerant passage connected to an evaporator outlet, a pressure regulator which controls an amount of refrigerant gas flowing into the refrigerant suction chamber by regulating a differential pressure between a pressure in the refrigerant suction chamber and a pressure in the crank chamber, the pressure regulator comprising a flow control valve including a first spring-loaded, normally-closed valve, a return spring permanently biasing the first valve to a fully-closed position, a spring chamber operably accommodating therein the return spring, and a pressure chamber accumulating a working pressure used to force the first valve toward a fully-opened position, the flow control valve provided in the low-pressure refrigerant passage upstream of the refrigerant suction chamber, and a flow control valve actuating mechanism including a communication passage through which the refrigerant discharge chamber communicates with the pressure chamber, a second spring-loaded, normally-closed valve provided in the communication passage, a return spring permanently biasing the second valve to a fully-closed position, and an electromagnetic solenoid controlling an opening of the second valve so that the opening increases with an increase in exciting current supplied to the solenoid, the second valve serving to introduce high-pressure refrigerant gas in the refrigerant discharge chamber into the pressure chamber as the working pressure with the opening controlled by the solenoid.
According to another aspect of the invention, a swashplate type variable-displacement compressor comprising a compressor housing which defines therein a crank chamber, a refrigerant suction chamber, a refrigerant discharge chamber, and a low-pressure refrigerant passage connected to an evaporator outlet, a pressure regulator which controls an amount of refrigerant gas flowing into the refrigerant suction chamber by regulating a differential pressure between a pressure in the refrigerant suction chamber and a pressure in the crank chamber, the pressure regulator comprising a flow control valve including a spring-loaded, normally-closed spool valve, a return spring permanently biasing the spool valve to a fully-closed position, a spring chamber operably accommodating therein the return spring, and a pressure chamber accumulating a working pressure used to force the first valve toward a fully-opened position, the flow control valve provided in the low-pressure refrigerant passage upstream of the refrigerant suction chamber, and a flow control valve actuating mechanism including a communication passage through which the refrigerant discharge chamber communicates with the pressure chamber, a second spring-loaded, normally-closed pilot valve provided in the communication passage, a return spring permanently biasing the pilot valve to a fully-closed position, and an electromagnetic solenoid controlling an opening of the pilot valve so that the opening increases with an increase in exciting current supplied to the solenoid, the pilot valve serving to introduce high-pressure refrigerant gas in the refrigerant discharge chamber into the pressure chamber as the working pressure with the opening controlled by the solenoid, and the flow control valve including a pressure regulating passage which escapes or channels the working pressure in the pressure chamber into the refrigerant suction chamber, and a flow-constriction means which serves to generally fully close the pressure regulating passage when the spool valve is held at the fully-opened position. It is preferable that the pressure regulating passage may comprise a communication passage through which the spring chamber of the flow control valve communicates with the refrigerant suction chamber, and a flow-constriction passage formed in the spool valve to intercommunicate the pressure chamber and the spring chamber. More preferably, the variable-displacement compressor may further comprise a stopper provided in the spring chamber to limit the fully-opened position of the spool valve and to close an opening end of the flow-constriction passage facing the spring chamber by abutment between the spool valve and an end face of the stopper when the spool valve is held at the fully-opened position. Also, the flow-constriction means may comprise a flow-constriction orifice groove formed on at least one of the end face of the stopper and the opening end of the flow-constriction passage facing the spring chamber to provide a flow-constriction orifice having a predetermined orifice size smaller than a flow-constriction passage area of the flow-constriction passage under a condition in which the fully-opened position of the spool valve is limited by abutment between the spool valve and the end face of the stopper. Preferably, the spool valve has a spool groove, and a pressure-receiving surface area of one side wall of the spool groove is dimensioned to be equal to a pressure-receiving surface area of the other side wall of the spool groove. It is preferable that the flow control valve actuating mechanism may further comprise a feedback means which detects a change in pressure in the evaporator outlet side of the low-pressure refrigerant passage upstream of the flow control valve to shift the pilot valve to either of a valve opening direction and a valve closing direction depending on the pressure change detected when the pressure change in the evaporator outlet side of the low-pressure refrigerant passage exceeds a predetermined allowable pressure change under a condition that the pilot valve is held at a given opening, so that an opening of the flow control valve is controlled and thus the pressure in the evaporator outlet side is kept constant. The flow control valve actuating mechanism may further comprise a pressure regulating passage through which the crank chamber communicates with the evaporator outlet side of the low-pressure refrigerant passage upstream of the flow control valve.
According to a still further aspect of the invention, a swashplate type variable-displacement compressor comprises a compressor housing which defines therein a crank chamber, a refrigerant suction chamber, a refrigerant discharge chamber, and a low-pressure refrigerant passage connected to an evaporator outlet, a pressure regulator which controls an amount of refrigerant gas flowing into the refrigerant suction chamber by regulating a differential pressure between a pressure in the refrigerant suction chamber and a pressure in the crank chamber, the pressure regulator comprising a flow control valve including a spring-loaded, normally-closed spool valve, a return spring permanently biasing the spool valve to a fully-closed position, a spring chamber operably accommodating therein the return spring, and a pressure chamber accumulating a working pressure used to force the first valve toward a fully-opened position, the flow control valve provided in the low-pressure refrigerant passage upstream of the refrigerant suction chamber, and a flow control valve actuating mechanism including a communication passage through which the refrigerant discharge chamber communicates with the pressure chamber, a second spring-loaded, normally-closed pilot valve provided in the communication passage, a return spring permanently biasing the pilot valve to a fully-closed position, and an electromagnetic solenoid controlling an opening of the pilot valve so that the opening increases with an increase in exciting current supplied to the solenoid, the pilot valve serving to introduce high-pressure refrigerant gas in the refrigerant discharge chamber into the pressure chamber as the working pressure with the opening controlled by the solenoid, and the flow control valve including a pressure regulating passage which channels the working pressure in the pressure chamber into the refrigerant suction chamber, and a fluid-flow passage shutoff means which serves to fully close the pressure regulating passage when the spool valve is held at the fully-closed position. Additionally, the fluid-flow passage shutoff means serves to fully close the pressure regulating passage even when the spool valve is held at the fully-opened position. It is preferable that the pressure regulating passage may comprise a communication passage formed in the housing accommodating therein the spool valve to communicate the pressure chamber with the refrigerant suction chamber there via, a recessed portion formed on an outer periphery of the spool valve which is communicatable with an opening end of the communication passage facing the pressure chamber depending on an axial position of the spool valve, and an orifice passage formed in the spool valve to communicate the recessed portion with the pressure chamber there via, and the recessed portion is formed on the outer periphery of the spool valve so that the recessed portion is brought into fluid-communication with the opening end of the communication passage facing the pressure chamber only when the spool valve is held within a predetermined valve opening range of the spool valve except for both the fully-closed position and the fully-opened position, so as to form the fluid-flow passage shutoff means by the spool valve itself. More preferably, the pressure regulating passage may comprise a communication passage through which the spring chamber of the flow control valve communicates with the refrigerant suction chamber, and a flow-constriction passage formed in the spool valve to intercommunicate the pressure chamber and the spring chamber. Preferably, the fluid-flow passage shutoff means may comprise a differential pressure valve provided in the flow-constriction passage to fully close the flow-constriction passage in response to a differential pressure between the pressure chamber and the spring chamber when the spool valve is held at the fully-closed position, and a stopper provided in the spring chamber to limit the fully-opened position of the spool valve and to close an opening end of the flow-constriction passage facing the spring chamber by abutment between the spool valve and an end face of the stopper when the spool valve is held at the fully-opened position. Alternatively, the flow-constriction passage may comprise a communication passage provided in the spool valve to intercommunicate the pressure chamber and the spring chamber, and a bushing fitted to one opening end of the communication passage and having an orifice passage.
The other objects and features of this invention will become understood from the following description with reference to the accompanying drawings.